The timer - You timed out! The alligator got you! Refers to a timeout timer that keeps a repeater from getting stuck on the air. If you talk for too long continuously, you'll cause the repeater to shut down temporarily (you timed out, or got bitten by the alligator). Most repeaters have timeouts of between 1 and 3 minutes. To avoid timing out, you must reset the timer. If you think you're getting close to the timeout point, and you are still mid-thought, just say "reset" or "let me reset" and unkey your mike briefly until you hear the reset beep (if the repeater has a beeper--most do), then continue talking where you left off. This requirement to pause periodically also keeps a repeater somewhat open and available for emergency or priority calls. That means you shouldn't get too long-winded and have to keep resetting the timer multiple times. Speak in shorter thoughts, then let the other person talk for a moment before you continue. This is especially important on a busy repeater where more than one person is involved in the conversation.
You're not making the machine! You've got the scratchies! You've got a lot of steam on your signal! - All terms that indicate your transmitter signal is weak into the repeater, and people are having trouble hearing you well. The "steam" comment simply refers to the "hiss" that comes out of a kettle. Try moving around a bit, or stepping outside (might be difficult in a moving car!). Incidentally, the interior of a car is terrible for a 2 meter walkie talkie. Your transmitted signal will have trouble getting out of the steel cage. It makes a huge difference to either stick the radio out your window (tough to talk on, though), or use an external antenna on the car.
You're full quieting! No noise on you! - The opposite of the above situation. Ways of saying that you sound just fine. Note that it is incorrect to ever say "You have my meter pinned" or "Receiving you full strength" on a repeater, since the person's signal on the other end is being retransmitted through the repeater. I once heard someone say, "I don't understand why your signal is so weak when I'm getting a full strength reading on my "S" meter here!" This only describes how strong the repeater's signal is to you, not the other guy's signal to the repeater.
Picket fencing refers to your signal rapidly going up and down in strength, and this is perceived by others as a fluttering sound that varies from slight to almost unintelligible. This is caused when you move about as you are transmitting. Most often a rapid fluttering happens when you are moving in a car. When you are standing or walking, you fade up and down slowly. It is the nature of radio signals, as they bounce off of various structures. Some things enhance your signal, others make it worse. Picket fencing is more pronounced when your signal is of marginal strength, meaning that your are some considerable distance laterally from the repeater. Either increase your power, get a better antenna system, or at least note that you may want to avoid using a particular repeater in that area due to your distance, or hills or buildings are getting in the way.
To kerchunk the machine is to click or hold down your mike button briefly--just long enough to cause the repeater to start up and transmit. This is a very common occurrence, but is actually illegal, strictly speaking. Such an act our your part would be classed as an "unidentified transmission" by the FCC, and such radio transmissions are illegal. If you're just checking to see if the repeater is working from your location, just drop in your call once, and you've complied with the law. You don't need to explain anything at all.
Jammers are infrequent, but they are an occasional fact of life. "Jammer" is an all-inclusive term that refers to someone that makes rude comments or continuously holds down their mike button (blocking access to the repeater and eventually causing it to time out. They never give proper identification, since what they are doing is both antisocial and illegal. A jammer is either a licensed ham with a personality deficit, someone who stole or somehow acquired a radio, or could possibly be a child of a licensed ham that decided to play with the radio. Whoever they are, rule #1 regarding jammers is: NEVER talk to or even acknowledge a jammer!! For rules number 2 through 10, please see rule #1 again!. It is illegal to cause willful interference, and some people unfortunately were not given enough hugs when they were babies. As a result, we sometimes have to deal with the consequences. If someone uses profanity, or refuses to identify themselves, just leave the air for a while. Don't talk to them or about them to anyone else. If you remove their soapbox by letting them hear nothing but silence as a response to their antics, they will usually get tired of it and go away. Please, please, PLEASE do not talk to, about, or encourage them in any way!
Things to do: Be polite, remember people's names (if you can), be a peacemaker, be a good conversationalist, be interesting and interested, offer help, offer your time to a good cause, offer support or money to help with the costs of operating such a wonderful repeater as (fill in the blank), give your call at least every 10 minutes (FCC requirement), get to know people and recognize their voices and calls, be ready to use phonetics to help people get your callsign or information right, make up interesting or funny phonetics for your callsign (the former head of Santa Clara County Communications is a ham: WA6UBE--"Whiskey After Six, Used By Everybody!" And she quite proudly says that!).
Things to avoid: Controversy, argumentative attitudes, strongly held (and defended) opinions, discussions about religion, sexual orientation, politics, race, Rush, Obama, etc. Also, once you get comfortable with the crowd on a particular repeater, avoid the temptation to constantly call your friends, or to chime in every single time on every single subject you feel strongly about. People will like you more if you are not "overdone" too much. Also, avoid at all costs using "10" codes, or anything that might make you sound like a refugee from the CB radio world. Replying to someone with "10-4" instead of "roger" or even just "Yep" runs the risk of attracting unpleasant verbal arrows (or at least bad karma). Hams do not hold CB'ers in high esteem, to say the least.
Other suggestions: Although you'll occasionally hear someone use "Q" signals, and you should be aware of a few of the most common ones, repeater operation is decidedly different than the ham communications you may have heard on the HF (shortwave: 3 to 30 MHz) bands. Down there, signals can be accompanied with noise, fading, beeps, squawks, and other impediments to intelligibility. With repeater operation, there is generally nothing but clear-sounding audio similar to what you might experience on the average telephone call. Hams are much more relaxed in their speech on repeaters. Avoid the use of lingo that you haven't already heard on the repeater. Instead of "handle", we just say "my name is...". We don't usually say, "You're 5 by 9", we just say you're nice and clear into the repeater. And never call "CQ" on a repeater! Instead, just drop in your call once, or at most say, "K7DAA monitoring", or "K7DAA listening" and you'll communicate the exact meaning you intended: "I'm here, and if anyone wants to talk, that'd be great!" If you don't hear anyone come back to you, don't be discouraged. Happens all the time. Just wait 10 minutes or more, and maybe say "K7DAA listening, northbound on 85 near Saratoga". That may induce someone to ask you more about the traffic there, or some related thing. I know one guy that says, "K6XXX, and it's a great day in West San Jose! The bees are buzzing, and the flowers are blooming!" He's in his late 80's and he's glad to be here for another day! He gets lots of "hellos" every day with that. To sum it all up, remember to just use plain conversational terms, and you'll be well understood and accepted.